Late twentieth century congressional leaders as shapers of and hostages to political context: Gingrich, Hastert, and Lott

Most contemporary explanations of congressional leadership postulate a version of contextual theory that typically places greatest emphasis on the strength of party and downplays the personal skills of individual leaders. By analyzing the leadership of just three recent individuals—Gingrich, Hastert, and Lott—this essay demonstrates the extent to which these leaders' different styles, skills, and characteristics interacted with changing political contexts and strategic environments to impact political and policy outcomes. Context matters, but so does leadership skill. Most graphically, Gingrich—a rare transforming leader in Burns' typology—demonstrates the importance of the right person and the right conditions being in place at the same time and the ability of an individual imaginative leader to intervene exogenously to have a significant effect on policy outcomes. Yet the essay also demonstrates that even where leaders adopt more conventional transactional styles, as Hastert and Lott did, the skill and success with which they juggle political pressures emanating from different, often conflicting, contexts—skills in context—also matters.

An algebra and conceptual model for semantic tagging of collaborative digital libraries

Cost-effective semantic description and annotation of shared knowledge resources has always been of great importance for digital libraries and large scale information systems in general. With the emergence of the Social Web and Web 2.0 technologies, a more effective semantic description and annotation, e.g., folksonomies, of digital library contents is envisioned to take place in collaborative and personalised environments. However, there is a lack of foundation and mathematical rigour for coping with contextualised management and retrieval of semantic annotations throughout their evolution as well as diversity in users and user communities. In this paper, we propose an ontological foundation for semantic annotations of digital libraries in terms of flexonomies. The proposed theoretical model relies on a high dimensional space with algebraic operators for contextualised access of semantic tags and annotations. The set of the proposed algebraic operators, however, is an adaptation of the set theoretic operators selection, projection, difference, intersection, union in database theory. To this extent, the proposed model is meant to lay the ontological foundation for a Digital Library 2.0 project in terms of geometric spaces rather than logic (description) based formalisms as a more efficient and scalable solution to the semantic annotation problem in large scale.

Special Section Guest Editorial: Image/Video Quality and System Performance

Rapid developments in display technologies, digital printing, imaging sensors, image processing and image transmission are providing new possibilities for creating and conveying visual content. In an age in which images and video are ubiquitous and where mobile, satellite, and three-dimensional (3-D) imaging have become ordinary experiences, quantification of the performance of modern imaging systems requires appropriate approaches. At the end of the imaging chain, a human observer must decide whether images and video are of a satisfactory visual quality. Hence the measurement and modeling of perceived image quality is of crucial importance, not only in visual arts and commercial applications but also in scientific and entertainment environments. Advances in our understanding of the human visual system offer new possibilities for creating visually superior imaging systems and promise more accurate modeling of image quality. As a result, there is a profusion of new research on imaging performance and perceived quality.

Interactions between physical activity and the environment to improve adolescent psychological wellbeing: a randomised controlled trial

Natural environments promote physical activity (PA) and are psychologically restorative. In adults, performing PA in nature provides additive benefits for self-esteem (SE). Studies in adolescents indicate no such effect. However, they have not examined the effect of interaction with natural environments. The aim of this study was to analyse the effects of exercising in natural and built environments on adolescent PA and SE. Sixty adolescents participated in a natural and built orienteering course in a randomised order. PA was assessed throughout whilst SE was assessed pre- and post-intervention. There was a significant effect for PA due to environment (P < 0.001) and sex (P < 0.01). Almost half the time in the natural environment was spent in moderate to vigorous PA, compared to a quarter in the built. The PA significantly improved SE (P < 0.05); however there was no environmental effect (P > 0.05). Natural environments should be used as a tool for engaging adolescents in PA.

Mitigate DoS and DDoS Attack in Ad Hoc Networks

This paper proposes a technique to defeat Denial of Service (DoS) and Distributed Denial of Service (DDoS) attacks in Ad Hoc Networks. The technique is divided into two main parts and with game theory and cryptographic puzzles. Introduced first is a new client puzzle to prevent DoS attacks in such networks. The second part presents a multiplayer game that takes place between the nodes of an ad hoc network and based on fundamental principles of game theory. By combining computational problems with puzzles, improvement occurs in the efficiency and latency of the communicating nodes and resistance in DoS and DDoS attacks. Experimental results show the effectiveness of the approach for devices with limited resources and for environments like ad hoc networks where nodes must exchange information quickly.